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727491b72a
This includes all test changes from
"Changing all cost calculation to be given in milliseconds"
and forwards.
Some of the things that caused changes in the result files:
- As part of fixing tests, I added 'echo' to some comments to be able to
easier find out where things where wrong.
- MATERIALIZED has now a higher cost compared to X than before. Because
of this some MATERIALIZED types have changed to DEPENDEND SUBQUERY.
- Some test cases that required MATERIALIZED to repeat a bug was
changed by adding more rows to force MATERIALIZED to happen.
- 'Filtered' in SHOW EXPLAIN has in many case changed from 100.00 to
something smaller. This is because now filtered also takes into
account the smallest possible ref access and filters, even if they
where not used. Another reason for 'Filtered' being smaller is that
we now also take into account implicit filtering done for subqueries
using FIRSTMATCH.
(main.subselect_no_exists_to_in)
This is caluculated in best_access_path() and stored in records_out.
- Table orders has changed because more accurate costs.
- 'index' and 'ALL' for small tables has changed to use 'range' or
'ref' because of optimizer_scan_setup_cost.
- index can be changed to 'range' as 'range' optimizer assumes we don't
have to read the blocks from disk that range optimizer has already read.
This can be confusing in the case where there is no obvious where clause
but instead there is a hidden 'key_column > NULL' added by the optimizer.
(main.subselect_no_exists_to_in)
- Scan on primary clustered key does not report 'Using Index' anymore
(It's a table scan, not an index scan).
- For derived tables, the number of rows is now 100 instead of 2,
which can be seen in EXPLAIN.
- More tests have "Using index for group by" as the cost of this
optimization is now more correct (lower).
- A primary key could be preferred for a normal key, even if it would
access more rows, as it's faster to do 1 lokoup and 3 'index_next' on a
clustered primary key than one lookup trough a secondary.
(main.stat_tables_innodb)
Notes:
- There was a 4.7% more calls to best_extension_by_limited_search() in
the main.greedy_optimizer test. However examining the test results
it looked that the plans where slightly better (eq_ref where more
chained together) so I assume this is ok.
- I have verified a few test cases where there was notable/unexpected
changes in the plan and in all cases the new optimizer plans where
faster. (main.greedy_optimizer and some others)
91 lines
3.9 KiB
Text
91 lines
3.9 KiB
Text
create table t1 (a int primary key, b int, c int, d int, e int, key ba (b,a), key bda (b,d,a), key cba (c,b,a), key cb (c,b), key d (d)) engine=aria;
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insert into t1 select seq,seq,seq,seq,seq from seq_1_to_10;
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insert into t1 values(20,2,2,2,2),(21,3,4,5,6);
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#
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# Get different scan costs
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#
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explain select sum(e) as "table_scan" from t1;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL NULL NULL NULL NULL 12
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Last_query_cost 0.012556
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explain select sum(a) as "index scan" from t1;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 index NULL PRIMARY 4 NULL 12 Using index
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Last_query_cost 0.007441
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#
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# Range scans should be used if we don't examine all rows in the table
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#
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explain select count(a) from t1;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
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Last_query_cost 0.000000
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explain select count(*) from t1 where a > 0;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range PRIMARY PRIMARY 4 NULL 12 Using where; Using index
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Last_query_cost 0.002795
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explain select count(*) from t1 where a > 1;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range PRIMARY PRIMARY 4 NULL 12 Using where; Using index
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Last_query_cost 0.002795
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explain select count(*) from t1 where a > 2;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range PRIMARY PRIMARY 4 NULL 11 Using where; Using index
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Last_query_cost 0.002665
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#
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# Shorter indexes are prefered over longer indexs
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#
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explain select sum(a+b) from t1;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 index NULL ba 9 NULL 12 Using index
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Last_query_cost 0.007441
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explain select count(*) from t1 where b between 5 and 10;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range ba,bda ba 5 NULL 6 Using where; Using index
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Last_query_cost 0.002015
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explain select sum(b+c) from t1 where b between 5 and 6 and c between 5 and 6;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range ba,bda,cba,cb cba 10 NULL 2 Using where; Using index
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Last_query_cost 0.001494
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# Cost of 'd' should be slightly smaller as key 'ba' is longer than 'd'
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explain select count(*) from t1 where b > 6;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range ba,bda ba 5 NULL 5 Using where; Using index
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Last_query_cost 0.001885
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explain select count(*) from t1 where d > 6;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range d d 5 NULL 5 Using where; Using index
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Last_query_cost 0.001885
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#
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# Check covering index usage
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#
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explain select a,b,c from t1 where a=b;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 index NULL cba 14 NULL 12 Using where; Using index
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Last_query_cost 0.007441
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#
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# Prefer ref keys over ranges
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#
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explain select count(*) from t1 where b=2;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ref ba,bda ba 5 const 2 Using index
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Last_query_cost 0.001059
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explain select count(*) from t1 where b=2 and c=2;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ref ba,bda,cba,cb cba 10 const,const 2 Using index
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Last_query_cost 0.001059
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explain select count(*) from t1 where b=3 and c between 3 and 4;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range ba,bda,cba,cb cba 10 NULL 2 Using where; Using index
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Last_query_cost 0.001494
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#
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# Prefer eq keys over ref keys
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#
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explain select a,b,e from t1 where a=10 or a=11;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range PRIMARY PRIMARY 4 NULL 2 Using index condition
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Last_query_cost 0.003126
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explain select a,b,e from t1 where d=10 or d=11;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range d d 5 NULL 2 Using index condition
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Last_query_cost 0.003126
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drop table t1;
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